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→INVESTIGATION 4: USING CONTROL FLOW STATEMENTS
# To generate a '''test error''', copy and paste the following '''test''' command:<br><span style="color:blue;font-weight:bold;font-family:courier;">[$number1 -gt $number2]</span><br><br>The reason for the error was that you need '''spaces''' between the '''square brackets''' and the '''test condition'''.<br><br>
# Copy and paste the following (correct) '''test''' command:<br><span style="color:blue;font-weight:bold;font-family:courier;">[ $number1 -gt $number2 ]</span><br><br>
# Issue a command to view the value of the '''exit status''' of the previously issued '''test''' command.<br>You should notice that is works properly.<br><br>Now that we have learned how to test conditions, let's learn about '''control-flow''' statements.<br><br>'''Logic statements''' are used to create '''different paths''' or directions that the shell script will take<br>based on the <u>result</u> of the '''test condition'''. In this tutorial,<br>we will only focus on the '''if''' and '''if-else''' logic statement.<br><br>[[Image:if-1.png|thumb|right|275px|Output of a shell script using the '''if''' command.]]
# Use a text editor like vi or nano to create the text file called '''if-1.bash''' (eg. <span style="color:blue;font-weight:bold;font-family:courier;">vi if-1.bash</span>)<br><br>If you are using the nano text editor, refer to notes on text editing in a previous week in the course schedule.<br><br>
# Enter the following lines in your shell script:<br><span style="font-family:courier;font-weight:bold;">#!/bin/bash<br>clear<br>num1=5<br>num2=10<br>if [ $num1 -gt lt $num2 ]<br>then<br> echo "Greater Than"<br>fi</span><br><br># Save your editing session and exit the text editor (eg. with vi: press '''ESC''', then type ''':wx''' followed by '''ENTER''').<br><br>[[Image:if-1.png|thumb|right|275px|Output of a shell script using the '''if''' command.]]
# Issue the following linux command to add execute permissions for your shell script:<br><span style="color:blue;font-weight:bold;font-family:courier;">chmod u+x if-1.bash</span><br><br>
# Run your shell script by issuing: <span style="color:blue;font-weight:bold;font-family:courier;">./if-1.bash</span><br><br>Confirm that the output indicated a correct result.<br><br>
